The subject matter disclosed herein relates generally to apparatuses and methods for mitigating vortex pumping of pressurization air in a turbine engine. More specifically, not by way of limitation, present embodiments relate to apparatuses and methods for mitigating vortex pumping effect on air pressure around an oil sump of a turbine engine.
In the turbine engine, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gases which flow downstream through turbine stages. These turbine stages extract energy from the combustion gases. A high pressure turbine includes a first stage nozzle and a rotor assembly including a disk and a plurality of turbine blades. The high pressure turbine first receives the hot combustion gases from the combustor and includes a first stage stator nozzle that directs the combustion gases downstream through a row of high pressure turbine rotor blades extending radially outwardly from a first rotor disk. In a two stage turbine, a second stage stator nozzle is positioned downstream of the first stage blades followed in turn by a row of second stage turbine blades extending radially outwardly from a second rotor disk. The stator nozzles turn the hot combustion gas in a manner to maximize extraction at the adjacent downstream turbine blades.
The first and second rotor disks are joined to the compressor by a corresponding rotor shaft for powering the compressor during operation. The turbine engine may include a number of stages of static air foils, commonly referred to as vanes, interspaced in the engine axial direction between rotating air foils commonly referred to as blades. A multi-stage low pressure turbine follows the two stage high pressure turbine and is typically joined by a second shaft to a fan disposed upstream from the compressor in a typical turbo fan aircraft engine configuration for powering an aircraft in flight.
As the combustion gasses flow downstream through the turbine stages, energy is extracted therefrom and the pressure of the combustion gas is reduced. The combustion gas is used to power the compressor as well as a turbine output shaft for power and marine use or provide thrust in aviation usage. In this manner, fuel energy is converted to mechanical energy of the rotating shaft to power the compressor and supply compressed air needed to continue the process.
One source of vortices in a turbine engine may be labyrinth seals which can create significant tangential velocity. This may be caused by viscous drag effects from the rotating components of the turbine engine, for example the seal or arm extending to support a seal. In an otherwise non-swirling fluid flow, the creation of these vortices can create significant pressure drop when associated with a change in radius of the swirling fluid. In many cases, such a pressure drop may be highly undesirable.
In certain oil sumps, minimum pressure differential may be used to prevent oil leakage and such pressure differential may be related to scavenge capability. When the pressure differential around a sump is too high, oil leakage prevention characteristics may be compromised. As utilized in the present disclosure, “pressure differential around a sump” may refer to the maximum difference in air pressure on the dry side of all oil seals for an individual sump.
The problem: In some oil sump configurations, excessive pressure differential around an oil sump may cause undesirable oil leakage.